Thyratron cathode design to prevent cleanup of hydrogen



Oct. 30, 1951 1 ROTHSTEIN 2,572,881

THYRATRON CATHODE DESIGN TO PREVENT CLEAN UP OF HYDROGEN Filed April 2'2, 1946 '4 f .z INVENTOR.

Janome ROTH snm ATTORNEY Patented Oct. 30, 1951 THY'RATRON CATHODE DESIGN T0 PRE- VENT CLEANUP OF HYDROGEN Jerome Rothstein, Barmer, N. J.

Application April 22, 1946, Serial No. 663,856

(ci. 31a-iso) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 8 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to a thyratron cathode arrangement which prevents clean up of hydrogen or other gas employed.

One object of this invention is to provide a cathode whose geometry is such that a reservoir of a hydride, or other suitable compound of the gas employed, is formed automatically during the processing oi the tube, or which compound is provided beforehand and which supplies hydrogen or other gas asy the gas in the tube cleans up.-

Another object is to provide such a thyratron cathode in which no special capsules or heater circuit arrangements are necessary.

Still another object is to provide such a thyratron cathode in which all ratings and characteristics are the same as the prototype tube.

These and other objects will become apparent in the specification and in the appended drawing in which:

Figure 1 is a vertical, cross-sectional View of the electrodes of the tube, and

Figure 2 is a vertical, cross-sectional view of the cathode and hydrogen reservoir within the cathode.

Referring to Fig. 1 which illustrates the assembled thyratron elements in perspective cross section showing a Well known arrangement in which a radiation shield I covers the major portion of the cathode assembly. The cathode is heated in the usual fashion by means of a heater wire Il wound spirally about the cathode body I2. The heater wire, which is preferably covered with a layer of insulating material such as aluminum oxide, is held against the cathode body by means of corrugated strips I3. 'I'he top of the cathode is preferably partially closed by inwardly extending annular disc member I4. The cathode is provided at its inner surface with a plurality of radial vanes I5 extending approximately half way to the center of the cathode body. Spaced from the inner ends of the vanes is a baille extension I6 which is attached to' and depends from a baille I1 supported on legs I8 abutting and attached to member I4. This baille extension is cylindrical in shape and is made preferably of nickel.

The entire cathode assembly is housed within, but insulated from, a cylindrical member I9 which carries screen 20 Welded, or otherwise suitably attached, to the screen are grid 2| and cover member 2l. Plate 22 is connected to lead 23 which together with the remainder of the structure shown is intended to be sealed in the Heating in vacuo converts the carbonates to oxide and allows reducing agents in the base metal to react with the oxides and free some barium, one of the alkaline earth metals. Conversion to oxide and activation of the cathode to produce free barium together constitute processing of the cathode according to conventional uses. Accordingly,'in one embodiment using hydrogen, during the processing of the tube the cathode is run overheated so that the barium is freed in the usual fashion from the conventional alkaline earth coating constituting the emitting surface of the cathode body I2 and vanes I5, the free barium being deposited onto the baille extension I6. The physical location of the baille is such that its upper end is maintained cool due to conduction and radiation from the baille and the feet, while the inner end is maintained quite hot due to the heating action of the cathode wires. Points intermediate the ends of the baffle extension are at temperatures intermediate the temperatures found at the respective ends.

At some zone along this extension, as at 25, the temperature will correspond to that of the correct hydrogen pressure from the dissociation of barium hydride formed in the tube when hydrogen is admitted. At points below 25 the the capsule is required as in the conventional barium hydride capsule. In addition, it is apparent, in this embodiment, that no barium hy- Another advantage lies in the fact that the barium' hydride formed on the extension is as reproducible as the cathode from which it is made. The reservoir zone, which corresponds to the outer surface of cylinder I6 in Fig. 1, is thus automatically maintained at the correct temperature for the desired pressure, and even if the tube is run at higher power with the cathode reaching higher than normal temperatures. the reservoir zone will automatically be driven to the region of desired temperature because of dissociation of the barium hydride and migration of the barium to a new region higher up than region 25 with recombination of the barium to form barium hydride.

Thus, there is provided a simple. economical and an elcient cathode geometry so modifled that barium hydride is formed automatically during the processing of the tube and which supplies hydrogen at practically the same rate as that at which the hydrogen in the tube cleans up.

In another embodiment which is illustrated in Fig. 2 member I6 is filled beforehand with a suitable hydride 200 such as titanium or zirconium hydride. The temperature distribution is substantially as described above and the mode of operation is the same, hydrogen now being replenished by dissociation of the hydride employed. For extremely high power applications this embodiment is preferable to the former because the high rate of hydrogen clean up may exceed the capabilities of the small reservoir described previously.

It is obvious that if a gas other than hydrogen is employed a suitable compound of that gas or material which absorbs that gas and is previously saturated therewith may be used in member I6 to provide by its dissociation or desorption respectively. gas to replenish that cleaned up during operation.

, While I have shown a single embodiment of the invention it is obvious that other shapes, arrangements and geometries are possible and will readily occur to those skilled in the art, and'I therefore do not intend to limit my invention except within the scope and extent of the appended claims.

I claim:

1. A hydrogen filled thermionic tube, including a metallic member supporting a hydride capable of releasing hydrogen upon being heated, a cathode spaced from said member and capable of heating a portion of said member, and a Y cooling baille connected to another portion of said member to establish a thermal gradient along said metallic member.

2. A hydrogen iilled thermionic tube including a thermionic cathode, a metallic member, one portion of which is positioned in heat radiation intercepting relationship with respect to said cathode, said member extending away from said cathode whereby another portion of said mem- 4 ber is beyond direct interception of said radiation, and a metallic hydride supported by said member.

3. A hydrogen-illled thermionic tube as defined in claim 2 wherein said hydride is barium hydride.

4. A hydrogen-filled thermionic tube as deiined in claim 2 in which said metallic member is a hollow, partially closed cylinder, and said metallic hydride is within said cylinder.

5. A hydrogen-illled thermionic tube including a metallic member mounted coaxially with the longitudinal axis of said tube, a hollow cathode surrounding said member, and a layer of barium hydride on the outer surface of said member for maintaining the operating hydrogen pressure in said tube.

6. A hydrogen-filled thermionic tube including a centrally-positioned metallic member, a hollow cathode surrounding said member but in spaced relationship from said member, whereby said member is heated by radiation intercepted from said cathode, and a metallic hydride deposited on the outer surface of said metallic member.

7. A hydrogen-filled thermionic tube including a cathode, a metallic member, one portion of which is positioned near the electron emitting surface of said cathode, another portion extending `beyond said cathode, a hydride of an alkaline earth metal supported by said member, one portion of said member being in heat-radiationintercepting relationship with respect to said cathode, a bale within said tube, Joined to said metallic member to be beyond direct interception of ysaid radiation, whereby a temperature gradient exists along said member, the range of said temperature gradient including the temperature for which the hydride is in equilibrium with the desired hydrogen pressure within said tube 8. A method of preparing a hydride reservoir for a hydrogen-filled thermionic tube provided with a metallic surface in the vicinity of a cathode, which includes ,the steps of preparing an electron-emitting coating on said cathode by converting alkaline earth carbonates to oxides, activating of said oxides with the resulting evaporation of the alkaline earth metallic byproducts, collecting and condensing a substantail portion of said by-products on said metallic surface and subsequently admitting hydrogen into said tube for combining said metallic byproducts with said hydrogen, thereby forming a reservoir of metallic hydride on said metallic surface.

JEROME ROTHSTEIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,740,700 Nickel et al. i Dec. 24, 1929 1,861,643 Pirani June 7, 1932 FOREIGN PATENTS Number Country Date I351,641 Great Britain July 2, 1931 

